BANGKOK — Antigovernment protesters in Bangkok girded themselves early on Saturday for clashes with the police as the government vowed to end their siege of the capital’s two commercial airports.

But there appeared to be reluctance among security forces to evict the protesters, forcing the government to abruptly demote the country’s national police chief on Friday.

Some 30 police vehicles lined a road leading to Suvarnabhumi International Airport, Thailand’s main gateway, and more than a dozen ambulances were parked beside the terminal.

“If the police come to crack down, let them do it,” Chamlong Srimuang, a 73-year-old protest leader and former army general, told cheering supporters. Protesters carried a large banner that read “Final Battle!!!” and stood behind razor wire and other obstacles placed in front of the main entrance to the airport.

The government did not explain the dismissal of Gen. Patcharawat Wongsuwan, the police chief, but a source in military intelligence who declined to be named because of the delicacy of the situation said the police chief was among a number of top security officials who have resisted the government’s orders to use force if necessary to clear the airports. The head of Bangkok’s metropolitan police force, Lt. Gen. Suchart Muankeaw, said he would follow the prime minister’s directives.

“The prime minister firmly ordered to take measures that would maintain a maximum of order and avoid clashes and damage,” General Suchart said.

There were conflicting reports over the extent of contacts between the government and protesters. The police said they had begun negotiations with protesters to end the standoff peacefully. But there also appeared to be back-channel negotiations. Mr. Chamlong said he received a call on Friday from an “important person” who pleaded unsuccessfully with him to end the protest.

Another protest leader, Sondhi Limthongkul, denied that any negotiation would take place with the government. “Ladies and gentlemen, please do not believe those rumors,” Mr. Sondhi said to the crowd at Suvarnabhumi airport.

At Don Muang, the city’s domestic airport, protesters stood on the sidewalk outside the blockaded terminal building, some wielding sticks.

Among them was Nattawan Taweechaipaisarnkul, 60, a gas station owner who carried crushed pepper kernels that she said she was ready to throw at police and swimming goggles as a defense against tear gas. “My daughter and son in the U.S. called me many times and told me not to go,” Mrs. Nattawan said. She said she slipped out of the house and told her family that she was going to the flea market.

After six months of uninterrupted protests, the followers of the People’s Alliance for Democracy, as the demonstrators call themselves, have had plenty of time preparing a climactic clash with the police. The group is well disciplined and enormously dedicated. But for the most part the people in the group are not hardened street fighters. At least half of the protesters gathered at the airports on Friday appeared to be middle-aged women. There were also many senior citizens and a smattering of children.

For all the damage that the airport sieges have done to Thailand’s international image, the protesters do not fit a portrait of revolutionaries. They have been deeply apologetic to the foreign tourists they inconvenienced after seizing the airports and went out of their way to offer them food. The government announced Friday that it would fly the stranded foreigners out of the country over the next few days and on Friday alone some 60 flights departed from the U-Tapao military airport, a two-hour drive from Bangkok.

In Thailand’s splintered society, it is difficult to gauge who still supports the protesters. The Bangkok Post, the English-language daily read by the establishment, called the seizure of the airports an “act of terrorism” but was also scathing about the government’s handling of the crisis.

The protesters wear yellow shirts to symbolize their allegiance to King Bhumibol Adulyadej, the ailing 80-year-old monarch who has ruled for the past six decades. But King Bhumibol has remained publicly silent about the airport seizures. Some analysts suggest that the protests must end by Friday, the king’s birthday, to spare him embarrassment.

Queen Sirikit, the monarch’s outspoken spouse, has been more public in airing her views. She expressed sympathy for the protesters by offering financial assistance to those injured during clashes in October with the police. And in what was seen as an extraordinary move, she attended the funeral of a protester who died from wounds apparently inflicted by the explosion of a tear-gas canister in October.

Protesters saw her attendance as a “green light” for their activities, said Thitinan Pongsudhirak, director of the Institute of Security and International Studies.

The conflict, Mr. Thitinan says, is rooted in a struggle for influence in the king’s waning years. “It takes place in the twilight of the king’s reign,” he said. “This is what this is all about. Who gets to rule Thailand?”

One of the leading complaints of protesters is that the crown prince, Maha Vajiralongkorn, was reportedly courted by Thaksin Shinawatra, the prime minister ousted in the September 2006 coup. Mr. Thaksin, a billionaire tycoon who still retains a loyal following in rural areas and among the poor, was seeking to subvert the monarchy, the protesters say. Mr. Thaksin is now in exile abroad and has been sentenced in absentia to two years in prison for abuse of power. But protesters say he still wields influence over the government of Prime Minister Somchai Wongsawat, who protesters want to step down.

Even after three years of on-again, off-again protests, passions remain high. A woman in a black shirt and yellow scarf who gave only her nickname, Oom, because she is a civil servant and afraid of reprisals, stood outside Don Muang airport on Friday and said she was prepared to fight. “I told my sister that I have come out to die,” she said. “I am ready to die.”

Janesara Fugal contributed reporting.

A version of this article appears in print on , on page A8 of the New York edition with the headline: Thai Protesters Maintain Airport Blockades and Prepare for Possible Clashes. Order Reprints|Today's Paper|Subscribe